外文翻译----有限元软件的发展

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1、Developing a Finite Element Analysis Agent Padmanabh Dabke Introduction Recently there is a trend towards using it in the early stages of design. A designer may use FEA just to validate the structural integrity of a design or she may use it for structural optimization along with the parametrized des

2、ign techniques.This paper examines the requirements of a structural analysis agent and proposes an architecture to facilitate FEA in a concurrent design environment. The next section briefly describes how FEA is used in a typical industrial set up.Section 3 presents a survey of existing FE tools. Se

3、ction 4 discusses some issues related to the development of an FEA agent. Section 5 proposes an architecture for the FEA agent that addresses the issues described in Section 4 and finally Section 6 presents the concluding remarks. Steps in Finite Element Analysis The process of FEA starts with ident

4、ification of the region of interest and the formulation of the physical problem。 1. The region of interest might be an assembly, a component or a portion of a component (or an assembly). The interaction of the rest of the assembly and the environmental conditions with the region of interest is captu

5、red in two ways. One way to represent this interaction is to idealize them as loads and displacement constraints on the region of interest. For example a spot weld fixing a component to a bigger structure will result in a constraining all the degrees of freedom at that point. The other commonly used

6、 method is to use spring and/or gap elements. Analysts often draw a Free Body Diagram of the region of interest to clarify its interaction with the rest of the assembly and to gain more insight into its structural behavior.Required components and assemblies are then retrieved from the Solid Modeling

7、 system into the finite element package.In recent years a number of commercial systems have started offering both: FEA and Solid Modeling capabilities. In this case, the data exchange may occur between two modules of the same package.The original design geometry is sometimes too complicated for the

8、purpose of analysis. The analyst may choose to simplify it so that it is easier to mesh and incurs less computational cost.This task of simplifying the design geometry is referred to as Global Idealization.Global Idealization may involve deletion/modification of some of the geometric features. The a

9、nalyst may choose to take advantage of the symmetry and analyze only a portion of the model. If the problem is axi-symmetric, she may choose to reduce a 3D problem to 2D by analyzing the radial cross-section.If the analyst intends to make significant modifications in the geometry, she may choose to

10、import the geometry in a drafting package first and then read the modified geometry in the analysis package.Global Idealization is often followed by Element Idealization. Element Idealization consists of characterizing the finite element dimensionality of the globally idealized object. The original

11、3D geometry may be transformed into a collection of 1D, 2D and 3D entities depending on the characterization of various geometric parts as beams, plates/shells, and solid elements respectively. Element Idealization decisions are based on two factors: shape of the object and the boundary conditions.

12、The next step in the modeling process is selection of type of elements and their material properties. Based on this decision, the user discretizes the idealized geometry into finite elements. This step is commonly referred to as Mesh Generation.Traditionally the loads and boundary conditions are app

13、lied to the nodes and the element boundaries. In the proposed system they are applied to the geometry. Finally, he user has to select the type of analysis (static, modal,etc.) and the solution method and the finite element model is ready for analysis. The raw answers computed by the finite element s

14、olver have to be processed further. This includes calculation of derived quantities (such as stress and strain values), computing error estimates, creating创建 graphical displays showing deformed shapes , stress contour plots, etc. All these tasks are collectively referred to as post-processing. Based

15、 on the post-processing results the user may modify the model at any stage of idealization (including the original design itself)and start the loop once again. An overview of the analysis process is shown in Figure 1. Figure 1 Steps in Finite Element Analysis Development of Finite Element Tools Due

16、to the obvious pay-offs associated with speeding up of the analysis process, there is almost an explosion of both research and commercial systems supporting FEA. The development of FEA tools has followed a path very similar to the development of Design Automation tools. The early software supporting

17、 FEA was primarily meant to automate tasks in the detailed analysis stage, namely Mesh Generation and Post-Processing. A survey of earlier work in automatic mesh generation methods can be found in references 2 and 3. Earlier mesh generator would simply discretize the analysis geometry into a bunch of elements with almost no regard for the solution accuracy implied by the mesh.Adaptive meshing methods improved the reliability of mesh generation process.These methods use one of the several error estimation techniques 4,5 to estimate the discretization error for a trial